<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
	.w {
		width: 1000px;
	}
		.box1 {
			height: 500px;
			margin: 0 auto;
			border: 1px solid red;
		}
		.box2 {
			width: 100%;
			height: 100px;
			position: absolute;
			top: 50px;
			right: 0;
		}
		.box3 {
			width: 1000px;
			height: 100%;
			margin: 0 auto;
		}
	</style>
</head>
<body>
	<div class="box1 w">
		<div class="box2">
			<div class="box3"></div>
		</div>
	</div>
</body>
</html>